If we're talking "thread drift" then EC261 is THE classic case.
It started out with the best of intentions to force airlines to face the true costs of overbooking by forcing them to compensate distressed passengers adequately.
It's now drift well out of the galaxy of Common Sense and into a void where ANY delay caused by virtually ANYTHING is ground for compensation.
We buy cars, fridges, TVs and a myriad of complex mechanical devices, fully aware that there's a likelihood of their failing at some time in the near or distant future.
Yet when we book a ticket, we expect an airline to have a reserve aircraft and reserve crew ready for every eventuality, whether at its home base or downline.
Sometimes it makes sense to revisit legislation to make sure that it mirrors the original intent....